Recording medium, reproducing apparatus, and reproducing method

ABSTRACT

In a recording medium on which is recorded a multiplexed stream including a plurality of first packets (V_main) constituting a first I-picture in a first video stream and a plurality of second packets (V_sub) constituting a second I-picture in a second video stream, information for identifying the first I-picture and information for identifying the second I-picture are recorded on the medium. A recording medium can thereby be obtained that enables the rapid detection, from a small amount of information, of a particular picture included in a stream such as a TS in which multiple content streams are multiplexed.

This application is a Divisional of copending application Ser. No.13/158,964 filed on Jun. 13, 2011, which is a Divisional of copendingapplication Ser. No. 11/665,621 filed on Apr. 18, 2007 (now U.S. Pat.No. 8,027,563 B2), which is the National Phase of PCT InternationalApplication No. PCT/JP2006/011292 filed on Jun. 6, 2006, which claimsbenefit to Patent Application No. JP2005-232619 filed in Japan, on Aug.10, 2005. The entire contents of all of the above applications arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a recording medium, more particularlyto a disc recording medium enabling the rapid location of data fordisplaying images in each of a plurality of streams recorded on therecording medium.

BACKGROUND ART

When content such as program or movie content is recorded on a recordingmedium, the video data of the content are coded by a coding method suchas the MPEG (Moving Picture Experts Group) method to create a videostream. The audio data of the content are coded by a method such as theAC-3 method to create an audio stream. In the MPEG-2 system stipulatedin ISO/13818, the video stream and the audio stream are multiplexed intoa TS (Transport Stream). The video data or audio data in the videostream or audio stream are broken up into 188-byte source packets, whichare the minimum units of access. In the description below, video streamsand audio streams will also be referred to simply as ‘streams’.

A video stream is made up of GOPs (Groups of Pictures), where a GOP isabout 0.5 seconds in terms of video reproduction time. A GOP comprisesI-pictures obtained by intra-frame coding, P-pictures obtained byinter-frame predictive coding in the forward direction, and B-picturesobtained by bidirectional predictive coding (in the description below,the term ‘picture’ will be used as a general term for I-pictures,P-pictures, and B-pictures).

An I-picture is placed at the beginning of a GOP. The I-picture at thebeginning of a GOP is also treated as an access point: a position atwhich random access to the video stream is possible. The I-picture atthe beginning of every GOP does not necessarily become an access point;if a plurality of GOPs constitute one access unit, for example, then theI-picture at the beginning of the first GOP among the plurality of GOPsis set as the access point.

In trick reproduction modes such as the fast-forward mode in which thevideo content is viewed by skipping from picture to picture, or when afunction such as time search is used to start the reproduction of thecontent from an intermediate point in the content specified by a time,in general, first an I-picture is decoded and reproduced. To performtrick reproduction etc. at higher speeds, it is necessary to detect thepositions of the I-pictures and their constituent source packetsquickly. The reason why trick reproduction starts with the decoding ofan I-picture is that until an I-picture is decoded, it is not possibleto decode other pictures.

The I-pictures in a stream are conventionally detected with reference toan EP_Map in which the display time information (PTS: Presentation TimeStamp) and I-picture positional information (SPN: Source Packet Number)are stored. An EP_Map is provided for every GOP (e.g., Patent Document1).

Information concerning the size of the I-pictures may be added to theabove PTS and SPN information, these data may be assembled into a tableand stored in the EP_Map, and the table stored in the EP_Map may bereferred to in order to detect the position and size of the I-picture(e.g., Patent Document 2).

-   Patent Document 1: Japanese Patent Application Publication No.    2002-158971 (pp. 38-40, FIG. 138)-   Patent Document 2: Japanese Patent Application Publication No.    2004-201034 (pp. 11-12, FIG. 5)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the invention described in Patent Document 1, however, although thePTS and SPN are detectable, the size of an I-picture is undetectable.Accordingly, after detecting the first of the source packetsconstituting an I-picture, the player or other reproducing apparatusmust decide whether each succeeding source packet belongs to theI-picture or not. In this case, reading an I-picture takes a long time.

In the invention described in Patent Document 2, when a plurality ofvideo streams are multiplexed into a single TS, the above table must beprovided separately for each video stream. In this case, the amount ofinformation in these tables assumes vast proportions, using up much ofthe storage space in the optical disc or other recording medium.Normally it is also necessary to store the tables in the memory of thereproducing apparatus before reproduction of the streams recorded on therecording medium. In this case, if the amount of information in thetables is vast as noted above, an increased amount of memory space isneeded to store the tables. The invention described in Patent Document 2accordingly leads to increases in the cost of the reproducing apparatusand the size of its circuitry.

As the uses of optical discs and other such media have diversified inrecent years, sometimes a plurality of video streams are recorded asparts of the same content on an optical disc. As a specific example,scenes of the making of a movie and comments by the director may bedisplayed simultaneously with the movie itself. In this case, two videostreams are multiplexed, one being the video stream of the movie, theother being the video stream of the movie-making scenes etc., and themultiplexed streams are recorded on the optical disc as a single stream.Video streams representing different programs may also be multiplexedand recorded on an optical disc as a single stream. In the inventions ofPatent Documents 1 and 2, however, much recording space is used indealing with this situation, leading to increases in the cost of theplayer or other reproducing apparatus and the size of its circuitry.

The present invention addresses the above problems with the object ofobtaining a recording medium enabling a particular picture included in astream such as a TS in which a plurality of video streams aremultiplexed to be found quickly from substantially the same amount ofinformation as in the past.

Means of Solution of the Problems

In a recording medium on which is recorded a multiplexed streamincluding a plurality of first packets constituting a first I-picture ina first video stream and a plurality of second packets constituting asecond I-picture in a second video stream, a recording medium accordingto the present invention has recorded thereon information foridentifying the first I-picture and information for identifying thesecond I-picture.

Effect of the Invention

According to the present invention a particular picture included in astream such as a TS in which a plurality of types of video streams aremultiplexed can be detected quickly from substantially the same amountof information as in the past.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram depicting the data structure of theoptical disc 102 in the first embodiment of this invention.

FIG. 2 schematically shows the logical file structure of the opticaldisc 102.

FIG. 3 is an explanatory diagram for giving a simplified description ofthe structure of a stream information file 231.

FIG. 4 is an explanatory diagram of the syntax of an address managementfile 222.

FIG. 5 is an explanatory diagram depicting the structure of thereproduction control information file 221.

FIG. 6 is an explanatory diagram of the syntax of the reproductioncontrol information file 221.

FIG. 7 is an explanatory diagram for giving a simplified description ofthe trick reproduction of programs etc. recorded on the optical disc 102in the first embodiment.

FIG. 8 (A), FIG. 8 (B), and FIG. 8 (C) schematically show therelationship between an address management file 222 and a streaminformation file 231.

FIG. 9 is an explanatory diagram depicting the relationship between astream information file 231 and its ‘SPN_GOP_Start’ 502 and ‘I_Pic_Size’503 information.

FIG. 10 (A) to FIG. 10 (D) are explanatory diagrams depicting imagesdisplayed when a plurality of video data streams are stored in a streaminformation file 231 and the video data are reproduced by a reproducingapparatus.

FIG. 11 (A) and FIG. 11 (B) are explanatory diagrams depicting the datastructure of a stream information file 231 in which a PIP stream isstored and the data structure of the address management file 222corresponding to the PIP stream, in a second embodiment.

FIG. 12 is an explanatory diagram of the syntax of the addressmanagement file 222 corresponding to a stream information file 231 inwhich a PIP stream is stored.

FIG. 13 is an explanatory diagram depicting trick reproduction based onan access point management table.

FIG. 14 is a block diagram showing the structure of a reproducingapparatus 100 for playing the optical disc 102.

FIG. 15 (A), FIG. 15 (B), and FIG. 15 (C) are explanatory diagramsshowing other examples of the information recorded in ‘I_Pic_Size’ 503and ‘I_Pic_Size_Sub’ 1200.

FIG. 16 (A) and FIG. 16 (B) is an explanatory diagram depicting the datastructure of a stream information file 231 in which a PIP stream isstored and the data structure of the address management file 222corresponding to the PIP stream, according to the third embodiment.

FIG. 17 is an explanatory diagram of the syntax of the access pointmanagement table 1610 in the third embodiment.

FIG. 18 is an explanatory diagram depicting trick reproduction based onthe access point management table 1610.

FIG. 19 (A), FIG. 19 (B), and FIG. 19 (C) are explanatory diagramsdepicting the recording of a size ID in the ‘I_Pic_Size’ 503,‘I_Pic_Size_Sub’ 1200, and ‘I_Start_Sub’ 1600.

EXPLANATION OF REFERENCE CHARACTERS

100 reproducing apparatus, 101 system control unit, 102 optical disc,103 reproducing drive unit, 110 demultiplexer, 111 main video decoder,112 sub video decoder, 113 audio decoder, 114 video mixer, 115 displayunit, 120 memory unit, 130 operation unit.

BEST MODE OF PRACTICING THE INVENTION First Embodiment

FIG. 1 is an explanatory diagram depicting the data structure of theoptical disc 102 in the first embodiment of this invention. Data arerecorded on the optical disc 102 from its inner circumference 201 to itsouter circumference 202. A lead-in area 210 in which startinginformation about the optical disc 102, its physical characteristics,and the like are recorded is disposed at the innermost circumference ofthe optical disc. Information about the file system of the optical disc102 (also referred to below as file system information) is recorded in amanagement information area 211 disposed just outside the lead-in area210 of the optical disc 102. Content data (TS etc.) is recorded by themanufacturer (content provider) in a user data area 212 disposed justoutside the management information area 211 in the optical disc 102.Information concerning the ending position of the optical disc 102 isrecorded in a lead-out area 213 disposed just outside the user data area212 of the optical disc 102.

The user data area 212 comprises a reproduction control information area220 and a stream information area 230. The stream information area 230comprises a plurality of stream information files 231 in which the TS'sare recorded in predetermined units. The reproduction controlinformation area 220 comprises one reproduction control information file221 and one (#1) or a plurality (#1, . . . , #N) of address managementfiles 222. The information recorded in the reproduction controlinformation file 221 includes information (play interval information)indicating the intervals on the stream to be reproduced incorrespondence to the content (hereinafter referred to as ‘playintervals’, described later), information indicating the order in whichthe plurality of streams specified by the play intervals are to bereproduced (reproduction order information), information relating to thecontent of the stream information files 231 (content information), etc.The content information is information giving, for example, the authorof the content.

The address management files 222 are in one-to-one correspondence withthe stream information files 231. Specifically, the address managementfiles 222 and stream information files 231 correspond by having, forexample, identical file names. The information recorded in an addressmanagement file 222 includes the starting addresses of the access pointsin the stream stored in the corresponding stream information file 231,the sizes of the I-pictures set as access points, and the PTS values ofthe I-pictures set as access points. FIG. 1 shows a configuration thathas one reproduction control information file, but the reproductioncontrol information file may be divided into a plurality of files on theoptical disc 102.

FIG. 2 schematically shows the logical file structure of the opticaldisc 102. The top stratum of this file structure is a root directory300. A disc directory 301 is subordinate to the root directory 300. Thereproduction control information file 221, an address managementdirectory 302, and a stream management directory 303 are subordinate tothe disc directory 301. The address management files 222 are subordinateto the address management directory 302, and the stream informationfiles 231 are subordinate to the stream management directory 303.

The reproduction control information area 220 shown in FIG. 1 comprisesthe reproduction control information file 221 and the address managementfiles 222 subordinate to the address management directory 302. Thestream information area 230 comprises the stream information files 231subordinate to the stream management directory 303.

As noted above, the address management files 222 are in correspondencewith the stream information file 231. In FIG. 2, the correspondence isindicated by identical file names: for example, the address control filerepresented by ‘01000.tmap’ in FIG. 2 corresponds to the streaminformation file represented by ‘01000.mts’. The notations ‘tmap’ and‘mts’ are extensions of the file names. Any file names may be used.

Although the address management files 222 and stream information files231 are shown located in separate directories in FIG. 2, the addressmanagement files 222 and the stream information files 231 may be locatedin the same directory. The address management files 222 and streaminformation files 231 may also be subordinate to the root directory 300(i.e., at the same hierarchical level as the disc directory).Furthermore, although the address management files 222 and streaminformation files 231 in FIG. 2 were described as correspondingone-to-one, one address management file 222 may correspond to aplurality of stream information files 231, or a plurality of addressmanagement files 222 may correspond to one stream information file 231.

FIG. 3 is an explanatory diagram that will be used to give a simpledescription of the structure of a stream information file 231. A streaminformation file 231 comprises a plurality of source packets 400 (asource packet 400 may be simply referred to as a packet 400 below). Morespecifically, a stream information file 231 comprises a multiplexedplurality of packets 400 obtained by coding the video data and audiodata of the aforesaid content, then dividing the coded data into fixedamounts of information (a packet 400 of video data will also be referredto as a V-packet (Video-packet) and a packet 400 of audio data will alsobe referred to below as an A-packet (Audio-packet) below).

Each packet 400 comprises a data area 403 in which video data or audiodata are recorded, and header information 401 in which is recorded an ID(Identification) 403 corresponding to the type of data recorded in thedata area. Accordingly, if the packet is a V-packet, for example, videodata are recorded in the data area 403, and an ID 402 indicating thatthe packet 400 is a V-packet is recorded in the header information 401.The header information 402 is prefixed at the front of the packet.

FIG. 4 is an explanatory diagram of the syntax of an address managementfile 222. The PTS (Presentation Time Stamp) indicating the startingdisplay time of the first picture in the stream information file 231corresponding to the address management file 222 is recorded in‘Start_PTS’. The PTS indicating the ending display time of the lastpicture in this stream information file 231 is recorded in ‘End PTS’.The total number of video streams in the stream information file 231 isrecorded in ‘num_of_video’ 500. The total number of audio streams in thestream information file 231 is recorded in ‘num_of_audio’.

The first loop statement (for(i=0; . . . ){ . . . }) following‘num_of_audio’ is repeated for the number of times indicated by‘num_of_video’ 500. The second loop statement (for(j=0; . . . ){ . . .}) following the first loop statement is repeated for the number oftimes indicated by ‘num_of_audio’. The ID of each V-packet and A-packetin the stream information file 231 is recorded in the ‘packet_ID’ fieldsin the loop statements. The ID of each V-packet and A-packet isaccordingly detected by execution of these loop statements in thereproducing apparatus (described later) or other apparatus thatreproduces the optical disc 102.

Information necessary for detecting a position specified during trickreproduction or a time search (i.e. information regarding an accesspoint) is recorded in an access point management table 510. For example,when the video data corresponding to the content is coded into a videostream according to MPEG-2, the start of a GOP is an access point.

The item ‘num_of_entry’ indicates the total number of access points inthe stream information file 231 corresponding to the address managementfile 222. The loop statement following ‘num_of_entry’ is repeated forthe number of times indicated by ‘num_of_entry’. The PTS indicating thestarting display time of an I-picture used as an access point isrecorded in ‘PTS_GOP_Start’ 501 in the loop statement. PTS valuescorresponding to source packet numbers X1, X2, and Xk are represented byPTS(x1), PTS(x2), and PTS (xk), respectively. ‘SPN_GOP_Start’ 502indicates the number of packets from the first packet in the streaminformation file 231 to the first packet among the packets constitutingthe I-picture (the position of this packet will also be referred tobelow as ‘the start of the access point’).

Since a packet has a fixed length (188 bytes in MPEG-2), the number ofbytes from the start of the stream information file 231 to the start ofthe access point can be calculated by multiplying the value of‘SPN_GOP_Start’ 502 by the fixed length value. Accordingly, if the valueof ‘SPN_GOP_Start’ 502 is 5 (packets), for example, and the packetlength is 188 bytes, then the number of bytes from the start of thestream information file 231 to the start of the access point is:

5 (packets)×188 (bytes)=940 (bytes)

(where x is the multiplication symbol). The starting positions of anI-picture needed by the reproducing apparatus in trick reproduction or atime search can be located (cued) by referring to the ‘PTS_GOP_Start’501 and ‘SPN_GOP_Start’ 502 as explained above.

Information representing the size of an I-picture that is used as anaccess point is recorded in ‘I_Pic_Size’ 503. Specifically, the numberof packets from the packet indicated by ‘SPN_GOP_Start’ 502 to the lastpacket in the packets constituting the I-picture is recorded in‘I_Pic_Size’ 503. The size of the I-picture can accordingly be detectedby referring to ‘I_Pic_Size’ 503. Specifically, the size of theI-picture (the size expressed in bytes) can be obtained by multiplyingthe value (number of packets) indicated by ‘I_Pic_Size’ 503 by the sizeof the packet (188 bytes for MPEG-2).

FIG. 5 is an explanatory diagram depicting the structure of thereproduction control information file 221. The reproduction controlinformation file 221 comprises a plurality of titles 1 to N. One titlecorresponds to one item of content (program, movie, etc.). Specifically,the intervals (play intervals) used in reproduction of the content inthe streams recorded in the stream information files 231 are listedunder the titles.

A title may be configured in various ways: for example, it may list (1)one play interval in one stream information file 231; (2) a plurality ofplay intervals in one stream information file 231; or (3) play intervalsin a plurality of stream information files 231 (one or more playintervals being recorded in each of the plurality of stream informationfiles 231). FIG. 5 shows a case in which a play interval 1 in one streaminformation file (#1) and a play interval 2 in another streaminformation file (#2) are listed under title 1 (configuration (3)above).

A play interval is determined by the file name of the address managementfile 222 corresponding to the stream information file 231 to bereproduced and the reproduction starting point (Start_Time) andreproduction ending point (End_Time) in the stream information file 231.In the following description, the file name, the reproduction startingpoint, and the reproduction ending point will be referred tocollectively as play interval information.

FIG. 6 is an explanatory diagram of the syntax of the reproductioncontrol information file 221. In FIG. 6, the total number of contentitems recorded on the optical disc 102 is recorded in ‘num_of_Title’.The loop statement following ‘num_of_Title’ is repeated for the numberof times indicated by ‘num_of_Title’. Information about a title(attribute information), such as the total time of the title (i.e.,reproduction time of the content corresponding to the title), type ofcodec, and time and date of recording are recorded in ‘Title_Attribute()’ in the loop statement.

The total number of items of information about play intervals recordedunder the title is recorded in ‘num_of_Play_Interval’. The loopstatement following ‘num_of_Play_Interval’ is repeated for the number oftimes indicated by ‘num_of_Play_Interval’. The file name of the streaminformation file 231 to be reproduced is recorded in ‘stream_name’ 701in the loop statement. The reproduction start point is described in‘Start_Time’ 702, and the reproduction end time is described in‘End_Time’ 703. As described above, the play interval informationincludes information given by ‘stream_name’ 701, ‘Start_Time’ 702, and‘End_Time’ 703. The PTS values indicating the starting display time andending display time of a picture are recorded in ‘Start_Time’ 702 and‘End_Time’ 703, respectively. The player or other reproducing apparatuscan identify the interval to be reproduced (play interval) in the streamstored in the stream information file 231 from the information recordedin the reproduction control information file.

FIG. 7 is an explanatory diagram that will be used to give a simpledescription of the trick reproduction of content recorded on the opticaldisc 102 in the first embodiment. Times (PTS) are indicated on thehorizontal axis labeled ‘play interval’. The stream information file 231comprises one or more GOPs 800. A GOP 800 comprises I-pictures,P-pictures, and B-pictures (labeled I, P, and B). The size of anI-picture is indicated as ‘I_Pic_Size’. In this trick reproduction mode,the I-pictures in the GOP 800 in the stream information file 231 of thereproduced content are reproduced by skipping (from the end of onereproduced I-picture to the start of another I-picture).

FIG. 8 (A), FIG. 8 (B), and FIG. 8 (C) schematically show therelationship between the address management file 222 and the streaminformation file 231. In FIG. 8 (A), ‘V’ indicates a video packet and‘A’ indicates an audio packet. Among the packets 400 constituting eachGOP, the hatched packets are the packets at the beginning of the GOP(also referred to below as leading packets), and their source packetnumbers SPN are indicated as ‘X1’, ‘X2’, . . . , ‘Xk’. As shown in FIG.8 (B), a leading packet includes a transport packet header (TP_H), whichis the header information 401 stipulated by the MPEG standard. BesidesTP_H, the packet includes a PES header (PES_H) 821, a sequence header(SQ_H) 822, and an I-picture header (I_PIC_H) 824 indicating the firstbyte of the I-picture information starting from the SQ_H. The PTSindicating the starting display time of the picture is recorded in thePES header 821.

The reproducing apparatus interprets the syntax of the addressmanagement file 222 described with reference to FIG. 4 to construct anaccess point management table 510 with an entry for each GOP (eachaccess point) giving its ‘PTS_GOP_Start’ 501, which is the PTS of thestarting display time of its I-picture, ‘SPN_GOP_Start’ 502, which ispositional information indicating the first source packet 400 among thepackets constituting the I-picture, and ‘I_Pic_Size’ 503, which isinformation indicating the size of the I-picture.

FIG. 9 is an explanatory diagram depicting the relationship between thestream information file 231 and its ‘SPN_GOP_Start’ 502 and ‘I_Pic_Size’503 information. As shown in FIG. 9, the stream information file 231comprises a plurality of GOPs 800. A GOP 800 comprises a plurality ofpictures. A picture comprises a plurality of source packets 400. Thereare two types of packets 400, i.e., V-packets corresponding to videodata (V_main packets in FIG. 9) and A-packets corresponding to audiodata. A stream information file 231 is therefore an area in whichmultiplexed streams of V-packets and A-packets are stored.

In FIG. 9, the symbols in parentheses in the picture notations indicate:(1) the type of packets constituting the picture; (2) the type ofpicture, that is, whether the picture is an I-picture, P-picture, orB-picture; and (3) the position of the picture relative to the start ofthe GOP. For example, ‘P(M_P_(—)04)’ indicates that the picturecomprises V_main packets, the picture is a P-picture, and the picture isthe fourth picture from the start of the GOP.

The symbols in parentheses in each V-packet indicate: (1) the type ofpicture to which the V-packet belongs, i.e., whether the picture is anI-picture, P-picture, B-picture; and (2) the position of the picturerelative to the start of the GOP. For example, ‘V_main(P_(—)04)’indicates that the V_main packet is part of a P-picture and theP-picture is the fourth picture from the start of the GOP.

‘SPN_GOP_Start’ 502 indicates the relative number of packets from thestart of the stream information file 231. For example, if the firstpacket in the first GOP in the stream information file 231 in FIG. 9 isalso the first packet in the stream information file 231, then‘SPN_GOP_Start’ 502 is ‘1 (packet)’. ‘I_Pic_Size’ 503 indicates therelative number of packets from the point specified by ‘SPN_GOP_Start’502 in the stream information file 231 to the last V-packet in theI-picture. For example, if the source packets 400 constituting theI-picture in the first GOP in the stream information file 231 aresituated within the thirteen source packets 400 starting from the firstpacket in the stream information file 231 (the packet position specifiedby ‘SPN_GOP_Start’ 502 in FIG. 9), then ‘I_Pic_Size’ 503 is ‘13(packets)’. Although ‘SPN_GOP_Start’ 502 and ‘I_Pic_Size’ 503 representrelative numbers of packets in the above description, ‘SPN_GOP_Start’502 and ‘I_Pic_Size’ 503 may represent relative numbers of bytes. Thatis, the result of multiplication of the number of packets and theabove-mentioned fixed length may be recorded in ‘SPN_GOP_Start’ 502 and‘I_Pic_Size’ 503.

In the above description, the stream stored in the stream informationfile 231 is described as a video stream comprising one type of V-packet(V_main) (there is only one type of video stream), but a plurality ofvideo streams may be multiplexed into one stream and stored in thestream information file 231. Next, the structure of the streaminformation file 231 etc. in a case in which a plurality of videostreams are multiplexed and stored will be described.

FIG. 10 (A) to FIG. 10 (D) are explanatory diagrams depicting a videodisplay when a plurality of video data streams are stored in a streaminformation file 231 and video pictures corresponding to the pluralityof video data streams are reproduced by a reproducing apparatus. In thefollowing description, two video streams are stored in the streaminformation file 231. One of these streams will be referred to as thefirst video stream or main video stream, and the other video stream willbe referred to as the second video stream or sub video stream. The videoimage corresponding to the first video stream will be referred to as thefirst video image or main video image, and the video image correspondingto the second video stream as the second video image or sub video image.Alternatively, one of the first or second video streams may support HD(High Definition), while the other video stream supports SD (StandardDefinition).

FIG. 10 (A) shows a case in which only the main video image isdisplayed; the letters ‘Main’ indicate main video. FIG. 10 (B) shows aPIP (Picture In Picture) display in which the sub video data (‘Sub’indicates sub video) are superimposed on the main video data. FIG. 10(C) shows a PIP display in which the main video data are superimposed onthe sub video data. FIG. 10 (D) shows a case in which only the sub videoimage is displayed. When two video streams are stored in the streaminformation file 231, there are four possible video display modes asdescribed above. In a PIP display, the size, the position, and thedegree of transparency of the superimposed region can be setarbitrarily. In the following description, a stream in which packetscorresponding to a plurality of video streams are multiplexed will alsobe referred to as a PIP stream.

FIG. 11 (A) and FIG. 11 (B) are explanatory diagrams depicting the datastructure of a stream information file 231 in which a PIP stream isstored and the data structure of a first-embodiment address managementfile 222 corresponding to the PIP stream. As shown in FIG. 11 (A), thestream information file 231 in which the PIP stream is stored comprisesmultiplexed V-packets corresponding to a plurality of video streams.Specifically, the stream information file 231 places main video pictures(I(M_I_(—)01) etc.) and sub video pictures (I(S_I_(—)01) etc.) in oneGOP, as shown in the picture layer in FIG. 11 (A). Therefore, as shownin the packet layer in FIG. 11 (B), the V_main packets constituting themain video stream and V_sub packets constituting the sub video streamare multiplexed in the PIP stream. In the part of the packet layercorresponding to picture I(S_I_(—)01) in FIG. 11 (A), V_main(I_(—)01)packets belonging to picture I(M_I_(—)01), V_sub(I_(—)01) packetsbelonging to picture I(SI_I_(—)1), and V_main(B_(—)02) packets belongingto picture B(M_B_(—)02) are intermixed.

The symbols in parentheses in the picture notations in FIG. 11 (A)indicate: (1) the video stream to which the picture belongs (main videoor sub video); (2) the type of picture, that is, whether the picture isan I-picture, P-picture, or B-picture; and (3) the position of thepicture in the GOP 800 relative to the first picture (I-picture) in thevideo stream. The symbol ‘S’ is assigned to sub video constituents andthe symbol ‘M’ is assigned to main video constituents. For example,‘B(S_B_(—)02)’ indicates that the picture is a sub video picture, thepicture is a B-picture, and the picture is the second of the sub videopictures in the GOP.

The symbols in parentheses in the V_main packet notation indicate: (1)the type of picture to which the V-packet belongs, that is, whether theV-packet is part of an I-picture, P-picture, or B-picture; and (2) theposition of the picture in the GOP relative to the start of the GOP. InFIG. 11 (A), ‘V_main’ indicates a V-packet in the main video stream and‘V_sub’ indicates a V-packet in the sub video stream. For example,‘V_sub(P_(—)15)’ indicates that the V-packet is part of the sub videostream, that the V-packet is part of a P-picture, and that this pictureis the fifteenth sub video picture in the GOP, counting from the subvideo I-picture.

Each packet comprises the same type of header information as the headerinformation 401 shown in FIG. 3. As an ID similar to the ID 402 shown inFIG. 3, the header information includes an ID indicating whether thepacket is an audio data packet, a main video packet, or a sub videopacket.

When a V_main packet and a V_sub packet have the same PTS value, theV_sub packet is located after the V_main packet.

Although the V_main packets and V_sub packets are intermingled in thestream described above, all the V_main packets may be located in apredefined segment of the stream, and all the V_sub packets may belocated in another predefined segment of the stream. The packets in astream stored in a stream information file 231 may be disposed in anyarrangement that satisfies the requirements of the decoder modelspecified in the MPEG standard. Provided these requirements aresatisfied, the arrangement can be set arbitrarily.

In trick reproduction using the above PIP stream, the main videoI-pictures (M_I-pictures) and sub video I-pictures (S_I-pictures) needto be detected at high speed. If the main video stream and the sub videostream were to have separate address management files 222, the relatedamount of information would increase as described above. Therefore, inthe first embodiment, the address management file 222 is structured asfollows.

As shown in FIG. 11 (B), both the ‘I_Pic_Size’ 503 of M_I-pictures andthe ‘I_Pic_Size_Sub’ 1200 of S_I-pictures are recorded in the accesspoint management table 1210 in the address management file 222.‘I_Pic_Size_Sub’ 1200 indicates the position of the last V_sub packetamong the V_sub packets constituting the I-picture in the sub video data(V_sub(I_xx), where xx is a positive integer (1 or more). As shown inthe packet layer in FIG. 11 (A), ‘I_Pic_Size_Sub’ 1200 is indicated bythe relative number of packets counted from a starting point, thestarting point being the V_sub packet immediately following the V_mainpacket indicated by ‘I_Pic_Size’ 503. Alternatively, the relative numberof packets from the position of the first packet in the GOP 800,indicated by ‘PTS_GOP_Start’ 501, may be recorded in ‘I_Pic_Size_Sub’1200. As another alternative, the number of bytes from ‘PTS_GOP_Start’501 may be recorded in ‘I_Pic_Size_Sub’ 1200.

FIG. 12 is an explanatory diagram of the syntax of the addressmanagement file 222 corresponding to a stream information file 231 inwhich a PIP stream is stored. Descriptions of syntax items other thanthe access point management table 1210 will be omitted because theywould be the same as the descriptions given for FIG. 4. Therefore, FIG.12 shows only the access point management table 1210. In the followingdescription, explanations of notation that was explained in FIG. 4 willbe omitted.

The loop statement (for(M=1 . . . ) following ‘I_Pic_Size’ 503 in FIG.12 is repeated {(value described in ‘num_of_video’ 500)−1} times foreach access point. In ‘I_Pic_Size_Sub’ 1200, the relative number ofpackets from the V_sub packet immediately following the V_main packetindicated by ‘I_Pic_Size’ 503 is recorded as information indicating theposition of the last V_sub packet among the V_sub packets constitutingan S_I-picture. By executing the loop statement, the reproducingapparatus detects one ‘I_Pic_Size_Sub’ 1200 for each sub video datastream stored in the stream information file 231.

Specifically, when one main video stream and one sub video stream aremultiplexed to form the stream stored in the stream information file231, b500 is ‘2’. In this case, the loop statement (for(m=1 . . . ) { .. . }) is executed just once. ‘I_Pic_Size_Sub’ 1200 is recorded in theaccess point management table 1210 for only one (=2−1) region as shownin FIG. 11 (B). When the stream includes only a main video stream (as inFIG. 9, for example), ‘num_of_video’ 500 is ‘1’. In this case, the loopstatement (for(m=1 . . . ) is not executed. The number of regions forwhich ‘I_Pic_Size_Sub’ 1200 is recorded in the access point managementtable 1210 is accordingly zero (=1−1). In other words, no such region ispresent.

FIG. 13 is an explanatory diagram depicting trick reproduction based onthe access point management table described with reference to FIG. 12.In the picture layer in FIG. 13, ‘I_Picture(Main)’ indicates a mainvideo I-picture, while ‘I_Picture(Sub)’ indicates a sub video I-picture.Trick reproduction of the PIP stream can be accomplished by reading theM_I-pictures of the main video stream and the S_I-pictures of the subvideo stream intermittently from the optical disc 102 and displayingthem simultaneously. ‘Simultaneous display’ means that the M_I-pictureand S_I-picture having PTS values indicating the same display time aredecoded substantially simultaneously, and the M_I-picture andS_I-picture are displayed simultaneously at the time specified by thePTS.

Specifically, ‘PTS_GOP_Start’ 501 and ‘SPN_GOP_Start’ 502 are used todetect the first of the V_main packets constituting the M_I-picture.‘I_Pic_Size’ 503 is used to detect the last of the V_Main packetsconstituting the M_I-picture. ‘I_Pic_Size_Sub’ 1200 is used to detectthe last of the V_sub packets constituting the S_I-picture. Then theinterval from the first V_main packet to the V_sub packet located at theposition with a packet number corresponding to the sum of the numbers ofpackets indicated by ‘I_Pic_Size’ 503 and ‘I_Pic_Size_Sub’ 1200 is readfrom the optical disc 102. By execution of the above process for eachaccess point, trick reproduction can be achieved by repeatedlyreproducing the I-pictures in the main video stream and the I-picturesin the sub video stream and skipping the other pictures, as shown inFIG. 13.

The process described above allows all the V_main packets of anM_I-picture and all the V_sub packets of an S_I-picture to be read atonce from the optical disc 102. As a result, high speed trickreproduction can be achieved in the display modes shown in FIG. 10 (B)and FIG. 10 (C).

FIG. 14 is a block diagram showing the structure of a reproducingapparatus 100 for playing the optical disc 102. Next, the operation ofthe reproducing apparatus 100 in reproducing a PIP stream in normalvideo reproduction mode will be described. The optical disc 102 isinserted into the reproducing drive unit 103. When the optical disc 102is inserted, the reproducing drive unit 103 reads the file systeminformation recorded in the management information area 211 of theoptical disc 102. The file system information is interpreted in thesystem control unit 101. The system control unit 101 then expands thelogical file structure of the optical disc 102 (FIG. 2).

Based on the expanded file structure, the system control unit 101controls the reproducing drive unit 103 so as to read the reproductioncontrol information file 221 and all the address management files 222recorded on the optical disc 102. The reproducing drive unit 103 outputsthe reproduction control information file 221 and address managementfiles 222 read from the optical disc 102 to the system control unit 101.The system control unit 101 stores the reproduction control informationfiles 221 and address management files 222 output from the reproducingdrive unit 103 in a memory unit 120.

Subsequently, when a user operates an manual operation unit 130 (e.g., aremote control) to select content to be reproduced by the reproducingapparatus 100, the system control unit 101 reads the title (FIG. 5)corresponding to the content from the reproduction control informationfile 221 stored on the memory unit 120. The system control unit 101 alsoreads the play interval information constituting the title of thecontent (the ‘stream_name’ 701, ‘Start_Time’ 702, and ‘End_Time’ 703 inFIG. 5) from the reproduction control information file 221. From thememory unit 120, the system control unit 101 reads the addressmanagement file 222 corresponding to the read-out play intervalinformation.

In reading the address management file 222, the system control unit 101searches for an access point in the PIP stream stored in a correspondingstream information file 231. Specifically, from among the‘PTS_GOP_Start’ information 501 recorded in the access point managementtable 1210 of the address management file 222, the system control unit101 detects the ‘PTS_GOP_Start’ 501 corresponding to the ‘Start_Time’702. Next, the system control unit 101 reads the ‘SPN_GOP_Start’ 502corresponding to the detected ‘PTS_GOP_Start’ 501 from the access pointmanagement table 1210, and acquires the position of the V_main packetcorresponding to the access point from the number of packets indicatedby ‘SPN_GOP_Start’ 502. The system control unit 101 controls thereproducing drive unit 103 so as to read the PIP stream stored in thestream information file 231 from the optical disc 102 sequentially,starting from the V_main packet corresponding to the access point.

The reproducing drive unit 103 reads the PIP stream stored in the streaminformation file 231 as directed by the reproducing drive unit 103 andoutputs it to the demultiplexer 110. The demultiplexer 110 separates theinput PIP stream into V_main packets, V_sub packets, and A-packets. Thedemultiplexer 110 separates packets from the PIP stream by sorting thepackets according to the ID (similar to the ID 402 shown in FIG. 3)recorded in the header information 401 of each packet. The reproducingdrive unit 103 outputs V_main packets to a main video decoder 111, V_subpackets to a sub video decoder 112, and A-packets to an audio decoder.

The main video decoder 111 outputs the data obtained by decoding theinput V_main packets (main video data) to a video mixer 114. The subvideo decoder 112 outputs the data obtained by decoding the input V_subpackets (sub video data) to the video mixer 114. The audio decoder 113outputs the data obtained by decoding the input A-packets (audio data)to a display unit 115. The main video decoder 111, sub video decoder112, and audio decoder 113 output data according to the time specifiedby the PTS recorded in the PES_H 821 (FIG. 8) of each packet.

For a PIP display, the video mixer 114 combines the main video data andsub video data output from the main video decoder 111 and sub videodecoder 112 according to the predefined size, position, and transparencyof the PIP window and outputs a signal corresponding to the combinedresult to the display unit 115. Based on the signal input from the videomixer 114, the display unit 115 displays the main and sub video picturesone within the other (see FIG. 10 (B) and FIG. 10 (C)). Together withthe display, the display unit 115 outputs sound based on the audio datainput from the audio decoder 113.

The video and audio components of the stream corresponding to one playinterval are reproduced by carrying out the process described above upto the time corresponding to ‘End_Time’ 703. If the title has aplurality of play intervals, the reproducing apparatus 100 carries outthe above process sequentially for each play interval. Reproduction ofthe content corresponding to the title ends when reproduction of thevideo and audio corresponding to the last play interval in the titleends.

During the above operations, the system control unit 101 outputs controlsignals 1111 as necessary to control the reproducing drive unit 103,demultiplexer 110, main video decoder 111, sub video decoder 112, audiodecoder 113 and video mixer 114.

Next, the operation of the reproducing apparatus 100 in a trickreproduction mode will be described. In the following description,descriptions of matters that are the same as in the normal reproductionmode will not be repeated.

When a user selects a trick reproduction mode by means of the manualoperation unit 130 during normal reproduction in the reproducingapparatus 100, the system control unit 101 detects and reads the addressmanagement file 222 corresponding to the stream information file 231being reproduced at the instant when the selection was made (theselection instant), to acquire the PTS (selection instant PTS)indicating the time on the PIP stream.

From the PTS_GOP_Start information 501 recorded in the access pointmanagement table 1210 in the address management file 222 it has read,the system control unit 101 searches for the closest ‘PTS_GOP_Start’ 501located after the selection instant PTS on the time axis. Based on the‘PTS_GOP_Start’ 501 it finds, the system control unit 101 acquires theinformation (‘SPN_GOP_Start’ 502, ‘I_Pic_Size’ 503, and ‘I_Pic_Size_Sub’1200) pertaining to the access point closest to the point on the PIPstream being reproduced at the selection instant.

From the acquired ‘PTS_GOP_Start’ 501 and ‘SPN_GOP_Start’ 502, thesystem control unit 101 detects the first V_main packet among the V_mainpackets constituting the MI-picture corresponding to the entry point tobe accessed next. From ‘I_Pic_Size’ 503, the system control unit 101detects the last V_main packet among the V_Main packets constitutingthis MI-picture. From ‘I_Pic_Size_Sub’ 1200, the system control unit 101detects the last V_sub packet among the V_sub packets constituting theSI-picture.

The system control unit 101 controls the reproducing drive unit 103 toread all the V_main packets corresponding to the MI-picture and all theV_sub packets corresponding to the S_I-picture from the optical disc102. The reproducing drive unit 103 reads the V-packets from the opticaldisc 102 as directed by the system control unit 101. Specifically, thereproducing drive unit 103 reads the packets (V_main packets, V_subpackets, and A-packets) from the V_main packet corresponding to‘SPN_GOP_Start’ 502 to the V_sub packet positioned at the packet numberequal to the value of the sum of the number of packets indicated by‘I_Pic_Size’ 503 and the number of packets indicated by ‘I_Pic_Size_Sub’1200, all at once.

By executing the process above for each access point, trick reproductionof the program can be achieved with a PIP display on the display unit115. Incidentally, although the above operations are performed for eachaccess point in the description above, in n-fold high-speed reproduction(where n is an integer or non-integer greater than zero), which is onetype of trick reproduction, some of the access points processed as abovecan be skipped, according to the value of n.

As described above, according to the optical disc in the firstembodiment, I-pictures can be rapidly retrieved from a stream such as aPIP stream that includes a multiplexed plurality of video streams, usingsubstantially the same amount of information as in conventionalretrieval.

In a multiplexed stream having a plurality of video streams, such as aPIP stream, all the packets constituting I-pictures in each video streamcan be retrieved rapidly. The I-pictures in each video stream cantherefore be read out at high speed. Even when a special type of displaysuch as a PIP display is carried out, accordingly, rapid trickreproduction can be achieved.

The optical disc 102 according to the first embodiment can greatlyreduce the amount of information (in the address management file 222)needed to retrieve sub video I-pictures. As noted above, the addressmanagement files 222 are stored in the memory unit 120 in thereproducing apparatus 100 before reproduction of the optical disc 102begins, but for reproduction of a PIP stream, with an optical disc 102according to the present embodiment, the amount of information in theaddress management files 222 stored in the memory unit 120 is small inoverall terms. Therefore, the circuit size of the memory unit 120 in thereproducing apparatus 100 can be reduced. The manufacturing cost of thereproducing apparatus 100 can accordingly be reduced. Furthermore, sincethe system control unit 101 has less data to process during trickreproduction, trick reproduction can be started quickly.

Next, the reduction in the amount of information in the addressmanagement files 222 will be described in specific terms. First, theamount of information in the access point management table will beestimated for the case in which a stream comprises just one type ofvideo stream.

First, it will be assumed that the reproducing apparatus 100 has a90-kHz system time clock. ‘PTS_GOP_Start’ 501 is measured in 90-kHzintervals, matching the system time clock. The amount of informationnecessary to represent ‘PTS_GOP_Start’ 501 for twenty-four hours withoutletting the counter (not shown) that counts system clock periods returnto zero (without wrapping around) can be calculated according to thefollowing equation (1).

90×10³ (Hz)×60 (seconds)×60 (minutes)×24 (hours)=7776000000  (1)

The value calculated by this equation (1) can be expressed in binarynotation by thirty-three bits. That is, the amount of informationnecessary to represent a twenty-four-hour ‘PTS_GOP_Start’ 501 isthirty-three bits. Next, if the storage capacity of the optical disc 102is assumed to be 50 GB, since the amount of information in one packet is188, the information necessary to represent ‘SPN_GOP_Start’ 502 for allpackets in the optical disc 102 can be calculated according to thefollowing equation (2).

50×10⁹ (bytes)/188 (bytes)≈265957447  (2)

The value calculated by this equation (2) can be expressed in binarynotation by twenty-eight bits. That is, the amount of informationnecessary to represent ‘SPN_GOP_Start’ 502 for all packets of theoptical disc 102 is 28 bits. Therefore, when one stream comprises justone type of video stream, the amount of information corresponding to oneentry in the access point management table is:

28 (bits)+33 (bits)=61 (bits)≈64 (bits)=8 (bytes).

When each GOP has a reproduction time of about 0.5 seconds and theI-picture in each GOP is an access point, there are 172,800 accesspoints (=60 (seconds)×60 (minutes)×24 (hours)/0.5 (seconds)) in a streamhaving twenty-four hours of reproduction time. Therefore, in order toprovide an eight-byte access point management table entry for eachaccess point, the following amount of information is necessary.

172,800 (access points)×8 (bytes)≈1.38 MB (megabytes)

Therefore, for a PIP stream including two multiplexed video streams, ifeach video stream were to have a separate access point management table,the following amount of information would be necessary.

1.38 (MB)×2 (video streams)=2.76 MB

In the optical disc 102 in the first embodiment, however, the pluralityof video data streams multiplexed in a PIP stream do not need to haveseparate access point management tables. The amount of informationneeded to retrieve I-pictures from the PIP stream can therefore besignificantly reduced.

Second Embodiment

In the first embodiment, the relative number of packets from the startof an access point is recorded in ‘I_Pic_Size’ 503, and the relativenumber of packets from the packet immediately following the packetcorresponding to ‘I_Pic_Size’ 503 is recorded in ‘I_Pic_Size_Sub’ 1200.In the second embodiment, the information recorded in ‘I_Pic_Size’ 503and ‘I_Pic_Size_Sub’ 1200 differs from that in the first embodiment. Inthe following description, explanations of matters explained in thefirst embodiment will be omitted.

FIG. 15 (A), FIG. 15 (B), and FIG. 15 (C) are explanatory diagramsshowing other examples of the information recorded in ‘I_Pic_Size’ 503and ‘I_Pic_Size_Sub’ 1200. FIG. 15 (A) schematically illustrates therelationship between a PIP stream 410 and the ‘I_Pic_Size’ 503 and‘I_Pic_Size_Sub’ 1200 described in the first embodiment. FIG. 15 (B)schematically illustrates the relationship between the PIP stream 410and the ‘I_Pic_Size’ 503 and ‘I_Pic_Size_Sub’ 1200 in the secondembodiment.

As explained above, in the first embodiment the relative number ofpackets from the start of an access point is recorded in ‘I_Pic_Size’503, and the relative number of packets from the packet immediatelyfollowing the packet corresponding to ‘I_Pic_Size’ 503 is recorded in‘I_Pic_Size_Sub’ 1200. In FIG. 15 (A), the ‘I_Pic_Size’ 503 recorded inthe access point management table is ‘13 (packets)’, which is the numberof packets from the V_main packet corresponding to ‘SPN_GOP_Start’ 502to the last V_main packet among the V_main packets constituting theM_I-picture. The ‘I_Pic_Size_Sub’ 1200 is ‘6 (packets)’, which is thenumber of packets from the V_sub packet immediately following the lastV_main packet among the V_main packets constituting the M_I-picture tothe last V_sub packet among the V_sub packets constituting theS_I-picture.

In FIG. 15 (B), a size ID representing the number of packets from theV_main packet corresponding to ‘SPN_GOP_Start’ 502 to the last V_mainpacket among the V_main packets constituting the M_I-picture is recordedas ‘I_Pic_Size’ 503 in an access point management table similar to theone in FIG. 11 (B). Another size ID, representing the number of packetsfrom the packet immediately following the packet corresponding to themaximum number of packets corresponding to the size ID of ‘I_Pic_Size’503 to the last V_sub packet among the V_sub packets constituting theS_I-picture, is recorded as ‘I_Pic_Size_Sub’ 1200.

A more concrete description will now be given. The I-picture size table1500 shown in FIG. 15 (C) is pre-stored in the memory unit 120 or othermemory means (not shown) in the reproducing apparatus 100. The I-picturesize table 1500 is a table that relates the size IDs to numbers ofpackets predefined as ‘I_Pic_Size’. For example, the relation in theI-picture size table 1500 shown in FIG. 15 (C) assigns 0 packets to sizeID ‘0’, 1 to 5 packets to size ID ‘1’, 6 to 10 packets to size ID ‘2’,11 to 15 packets to size ID ‘3’, 16 to 20 packets to size ID ‘4’, 21 to25 packets to size ID ‘5’, 26 to 30 packets to size ID ‘6’, and 31 ormore packets to size ID ‘7’.

In the access point management table, which is similar to the one shownin FIG. 11 (B), the size ID with the range including the number ofpackets from the V_main packet corresponding to ‘SPN_GOP_Start’ 502 tothe last V_main packet among the V_main packets constituting theM_I-picture is calculated with reference to the I-picture size table1500 and recorded as ‘I_Pic_Size’ 503. The size ID with the rangeincluding the number of packets from the packet immediately followingthe maximum number of packets corresponding to the size ID of‘I_Pic_Size’ 503 to the last V_sub packet among the V_sub packetsconstituting the S_I-picture is calculated with reference to theI-picture size table 1500 and recorded as ‘I_Pic_Size_Sub’ 1200.

For example, in FIG. 15 (B), since the number of packets correspondingto ‘I_Pic_Size’ 503 in FIG. 15 (A) is ‘13 (packets)’, the size ID ‘3’ isrecorded in ‘I_Pic_Size’ 503 in the second embodiment. However, althoughthe number of packets corresponding to ‘I_Pic_Size_Sub’ 1200 is ‘6(packets)’, the size ID recorded in ‘I_Pic_Size_Sub’ 1200 in FIG. 15 (B)is not ‘2’. A specific explanation will be given next.

The sum of the number of packets corresponding to the M_I-picture andthe number of packets corresponding to the S_I-picture is ‘19 (=13+6)’.As size ID ‘3’ is recorded in ‘I_Pic_Size’ 503, however, fifteen ofthese nineteen packets will be read from the optical disc 102. The sizeID recorded as ‘I_Pic_Size_Sub’ 1200 only has to cause four packets tobe read from the optical disc 102. In FIG. 15 (B), accordingly, the sizeID ‘1’ is recorded as ‘I_Pic_Size_Sub’ 1200.

Next, the operation of the reproducing apparatus 100 in a trickreproduction mode in the second embodiment will be described. In thefollowing description, explanations of operations explained in the firstembodiment will be omitted; only operations different from those in thefirst embodiment will be described. The system control unit 101 acquiresinformation (‘SPN_GOP_Start’ 502, ‘I_Pic_Size’ 503, ‘I_Pic_Size_Sub’1200) about the access point closest to the point on the PIP streambeing reproduced at the selection instant.

Based on the acquired ‘PTS_GOP_Start’ 501 and ‘SPN_GOP_Start’ 502, thesystem control unit 101 detects the first V_main packet among the V_mainpackets constituting the M_I-picture corresponding to the entry point tobe accessed next. The system control unit 101 acquires the size IDrecorded in ‘I_Pic_Size’ 503 (referred to below as the first size ID)and the size ID recorded in ‘I_Pic_Size’ 503 (referred to below as thesecond size ID). With reference to the I-picture size table 1500, thesystem control unit 101 calculates the sum (also referred to below asthe total number of packets) of the maximum number of packetscorresponding to the first size ID (e.g., 15 packet if this size ID is‘3’), and the maximum number of packets corresponding to the second sizeID. For example, in FIG. 15 (B), the system control unit 101 adds ‘15(packets)’, the maximum number of packets corresponding to the firstsize ID, and ‘5 (packets)’, the maximum number of packets correspondingto the second size ID, to find that twenty packets must be read from theoptical disc 102.

If the second size ID is ‘0’, only the packets indicated by the firstsize ID need be read from the optical disc 102. This is because when thesecond size ID is ‘0’, the range of packets indicated by the first sizeID includes all the V-packets constituting the sub video I-picture.

The system control unit 101 controls the reproducing drive unit 103 toread the number of packets indicated by the total number of packets,starting from the packet corresponding to ‘SPN_GOP_Start’ 502. Thereproducing drive unit 103 reads the packets from the optical disc 102as directed by the system control unit 101, thereby reading all theV_main packets of the M_I-picture and all the V_sub packets of theS_I-picture. In FIG. 15 (B), for example, the reproducing drive unit 103reads twenty packets, which is the sum of the maximum number of packetscorresponding to the first size ID (15 packets) and the maximum numberof packets corresponding to the second size ID (5 packets), startingfrom the packet corresponding to ‘SPN_GOP_Start’ 502.

As described above, in the optical disc 102 according to the secondembodiment, ‘I_Pic_Size’ 503 and ‘I_Pic_Size_Sub’ 1200 are specified byusing size IDs. The amount of information in the access point managementtable is therefore less than in the first embodiment. The amount ofinformation necessary to retrieve an M_I-picture and an S_I-picture canbe substantially the same as usual.

Whether to use the access point management table in the first embodimentor the access point management table in the second embodiment in anoptical disc 102 can be determined, for example, as follows.

In the access point management table in the first embodiment, the actualnumber of packets is recorded in ‘I_Pic_Size’ 503 and ‘I_Pic_Size_Sub’1200. Therefore, the system control unit 101 can detect the preciserange in which packets (V_main packets and V_sub packets) correspondingI-pictures are present in the PIP stream. The computational load on thesystem control unit 101 can therefore be reduced, because the processingperformed by the system control unit 101 is minimized.

In the access point management table in the second embodiment, size IDsare recorded in ‘I_Pic_Size’ 503 and ‘I_Pic_Size_Sub’ 1200. The systemcontrol unit 101 therefore detects an approximate range in which packets(V_main packets and V_sub packets) corresponding to I-pictures arepresent in the PIP stream. The system control unit 101 must accordinglyprocess a few more packets than the minimum necessary number. However,the amount of information in the access point management table in thesecond embodiment is smaller than in the first embodiment.

Therefore, if a reduction in computational load on the system controlunit 101 is desired, the access point management table of the firstembodiment may be adopted, and if a reduction in the area in the opticaldisc 102 necessary to record the access point management tables ispreferable in order to save space for other information on the opticaldisc 102, the access point management table of the second embodiment maybe employed.

In a PIP display of the type in FIG. 10 (B) or (C), as described in thefirst or second embodiment, an M_I-picture and an S_I-picture must bedisplayed simultaneously (at the same time). Therefore, the PTSindicating the starting display time of the M_I-picture and the PTSindicating the starting display time of the S_I-picture have identicalvalues (condition 1). The first V_sub packet in the V_sub packetsconstituting the S_I-picture is detected from ‘I_Pic_Size’ 503.‘I_Pic_Size’ 503 is set with reference to ‘SPN_GOP_Start’ 502.

The packets are arranged so that the first of the V_sub packetsconstituting the S_I-picture is always located after the first of theV_main packets constituting the M_I-picture. If the number of packetsfrom the first packet in the PIP stream to the first of the V_subpackets constituting the S_I-picture is SPNS, and the number of packetsfrom the start of the PIP stream to the first of the V_main packetsconstituting the M_I-picture is SPNM, then the packets are arranged sothat SPNS>SPNM (condition 2). By arranging packets to satisfy conditions1 and 2 above, a PIP display can be performed with one stream.

Third Embodiment

In the first embodiment, a case was described in which the V_mainpackets in the main video stream and the V_sub packets in the sub videostream were detected for trick reproduction during a PIP display (FIG.10 (B) or (C)). In the case to be described in the third embodiment,only the V_sub packets in the sub video stream are detected and only thesub video image is displayed (FIG. 10 (D)). In the followingdescription, explanations of matters explained in the first and secondembodiments will be omitted. In the drawings referred to in thefollowing description, the unexplained elements are indicated by thesame reference characters as in the drawings referred to in thedescriptions of the first and second embodiments.

FIG. 16 is an explanatory diagram depicting the data structure of astream information file 231 in which a PIP stream is stored and the datastructure of the address management file 222 corresponding to the PIPstream according to the third embodiment. As shown in FIG. 16, theaccess point management table 1610 recorded in the address managementfile 222 according to the third embodiment has an ‘I_Start_Sub’ column1600 in which the number of packets from the V_main packet correspondingto ‘SPN_GOP_Start’ 502 to the first V_sub packet among the V_sub packetsconstituting the S_I-picture is recorded.

Therefore, all V_sub packets constituting the S_I-picture are includedin a range from the packet corresponding to ‘SPN_GOP_Start’ 502 to thepacket identified by the number of packets equal to the sum of thenumber of packets recorded in ‘I_Pic_Size’ 503 and the number of packetsrecorded in ‘I_Pic_Size_Sub’ 1200, excluding the range from the packetcorresponding to ‘SPN_GOP_Start’ 502 to the packet identified by thenumber of packets recorded in ‘I_Start_Sub’ 1600.

FIG. 17 is an explanatory diagram of the syntax of the access pointmanagement table 1610 in the third embodiment. The loop statement(for(M=1 . . . ){ . . . }) following ‘I_Pic_Size’ 503 is repeated{(value recorded in ‘num_of_video’ 500)−1} times for each access point.By execution of the loop statement, ‘I_Pic_Size_Sub’ 1200 and‘I_Start_Sub’ 1600 are detected as many times as the number of sub videodata streams stored in the stream information file 231. In‘I_Pic_Size_Sub’ 1200, the relative number of packets from the V_subpacket immediately following the V_main packet indicated by ‘I_Pic_Size’503 is recorded as information indicating the position of the last V_subpacket among the V_sub packets constituting the SI-picture. In‘I_Start_Sub’ 1600, the relative number of packets from the V_mainpacket indicated by ‘SPN_GOP_Start’ 502 is recorded as informationindicating the position of the first V_sub packet among the V_subpackets constituting the SI-picture.

FIG. 18 is an explanatory diagram depicting trick reproduction based onthe access point management table 1610 described in FIG. 17. In thepicture layer of FIG. 18, ‘I_Picture(Main)’ represents a main videoI-picture, and ‘I_Picture(Sub)’ represents a sub video I-picture. Trickreproduction of the PIP stream as in the display shown in FIG. 10 (D)can be accomplished by intermittently reading the SI-pictures of the subvideo stream from the optical disc 102.

Specifically, ‘PTS_GOP_Start’ and ‘SPN_GOP_Start’ are used to detect thefirst of the V_main packets constituting the MI-picture (also referredto below as the leading V_main packet). ‘I_Pic_Size’ 503 is used todetect the last of the V_Main packets constituting the M_I-picture (alsoreferred to below as the terminal V_main packet). ‘I_Pic_Size_Sub’ 1200is used to detect the last of the V_sub packets constituting theS_I-picture (also referred to as the terminal V_sub packet).‘I_Start_Sub’ 1600 is used to detect the first of the V_sub packetsconstituting the S_I-picture (also referred to below as the leadingV_sub packet). The packets from the leading V_sub packet detected by‘I_Start_Sub’ 1600 to the terminal V_sub packet detected by the‘I_Pic_Size_Sub’ 1200 are read from the optical disc 102. The packets inthe minimum range necessary for reading the V_sub packets constitutingthe S_I-picture can thereby be obtained. By execution of the aboveprocess for each access point, trick reproduction can be performed byrepeatedly reproducing the S_I-pictures and skipping the other pictures,as shown in FIG. 18.

Next, the operation of the reproducing apparatus 100 in trickreproduction of a PIP stream displayed as shown in FIG. 10 (D) will bedescribed. In the following description, explanations of operationsexplained in the first embodiment will be omitted; only operationsdifferent from those in the first embodiment will be described. Thesystem control unit 101 acquires information (‘PTS_GOP_Start’ 501,‘SPN_GOP_Start’ 502, ‘I_Pic_Size’ 503, ‘I_Pic_Size_Sub’ 1200 and‘I_Start_Sub’ 1600) about the access point closest to the point on thePIP stream being reproduced at the selection time.

From the acquired ‘PTS_GOP_Start’ 501 and ‘SPN_GOP_Start’ 502, thesystem control unit 101 detects the first V_main packet among the V_mainpackets constituting the MI-picture corresponding to the entry point tobe accessed next. From ‘I_Pic_Size’ 503, the system control unit 101detects the last V_main packet among the V_main packets constitutingthis MI-picture. From ‘I_Pic_Size_Sub’ 1200, the system control unit 101detects the last V_sub packet among the V_sub packets constituting theSI-picture. From ‘I_Start_Sub’ 1600, the system control unit 101 detectsthe first V_sub packet among the V_sub packets constituting theSI-picture.

The system control unit 101 now controls the reproducing drive unit 103to read the packets in the range containing all the V_sub packets of theSI-picture, from the leading V_sub packet to the terminal V_sub packet,from the optical disc 102. The reproducing drive unit 103 reads theV-packets from the optical disc 102 as directed by the system controlunit 101. Specifically, the reproducing drive unit 103 reads theV-packets (V_main packets and V_sub packets) included in the range fromthe V_sub packet indicated by ‘I_Start_Sub’ 1600 to the V_sub packetindicated by ‘I_Pic_Size_Sub’ 1200 in the PIP stream, all at once.

As described above, with the optical disc 102 in the third embodiment,in a trick reproduction mode in which only the sub video image isdisplayed, as shown in FIG. 10 (D), the V_sub packets necessary fordisplaying the sub video image can be detected and read out rapidly.

With the access point management table according to the first or secondembodiment, all V_main packets constituting the MI-picture and all V_subpackets constituting the SI-picture are read from the optical disc 102at once. However, when only the sub video image is displayed, the V_mainpackets are not required. Therefore, when only the sub video image isdisplayed, simultaneous reading of V_sub packets and V_main packetsimposes unnecessary processing on the system control unit 101, resultingin an increased computational load on the system control unit 101.

The overall operation of the reproducing apparatus is hence delayed,which makes rapid trick reproduction of the sub video difficult.Therefore when only the sub video is displayed, at a minimum, all theV_sub packets necessary for display of the sub video must be read, butas far as possible, V_main packets should not be read. The optical disc102 according to the third embodiment can satisfy these requirementswith a simple structure.

Although the above operations are performed for each access point in thedescription above, in n-fold high-speed reproduction (where n is aninteger or non-integer greater than zero), which is one type of trickreproduction, some of the access points processed as above can beskipped, according to the value of n.

Fourth Embodiment

Although the third embodiment was described above as recording theactual number of packets in ‘I_Pic_Size’ 503, ‘I_Pic_Size_Sub’ 1200, and‘I_Start_Sub’ 1600 in, an I-picture size table 1500 can be used in thethird embodiment as in the second embodiment. This will now be describedspecifically. In the following description, explanations of mattersexplained in the first to third embodiments will be omitted.

FIG. 19 (A), FIG. 19 (B), and FIG. 19 (C) are explanatory diagramsdepicting the recording of size IDs in ‘I_Pic_Size’ 503,‘I_Pic_Size_Sub’ 1200, and ‘I_Start_Sub’ 1600. FIG. 19 (A) schematicallyillustrates the relationship between the PIP stream 410 and the‘I_Pic_Size’ 503, ‘I_Pic_Size_Sub’ 1200, and ‘I_Start_Sub’ 1600described in the third embodiment. FIG. 19 (B) schematically illustratesthe relationship between the PIP stream 410 and the ‘I_Pic_Size’ 503,‘I_Pic_Size_Sub’ 1200, and ‘I_Start_Sub’ 1600 in the fourth embodiment.

In FIG. 19 (A), the ‘I_Pic_Size’ 503 recorded in the access pointmanagement table is ‘13 (packets)’, which is the number of packets fromthe V_main packet corresponding to ‘SPN_GOP_Start’ 502 to the lastV_main packet among the V_main packets constituting the M_I-picture. The‘I_Pic_Size_Sub’ 1200 is ‘6 (packets)’, this being the number of packetsfrom the V_main packet immediately following the last V_main packetamong the V_main packets constituting the M_I-picture to the last V_subpacket among the V_sub packets constituting the S_I-picture. The‘I_Start_Sub’ 1600 is ‘9 (packets)’, which is the number of packets fromthe V_main packet corresponding to ‘SPN_GOP_Start’ 502 to the firstV_sub packet among the V_sub packets constituting the S_I-picture.

In FIG. 19 (B), a size ID representing the number of packets from theV_main packet corresponding to ‘SPN_GOP_Start’ 502 to the last V_mainpacket among the V_main packets constituting the M_I-picture is recordedas ‘I_Pic_Size’ 503 in the access point management table. Another sizeID, representing the number of packets from the packet immediatelyfollowing the packet corresponding to the maximum number of packetscorresponding to the size ID of ‘I_Pic_Size’ 503 to the last V_subpacket among the V_sub packets constituting the S_I-picture, is recordedas ‘I_Pic_Size_Sub’ 1200. Yet another size ID, representing the numberof packets from the packet corresponding to ‘SPN_GOP_Start’ 502 to thefirst V_sub packet among the V_sub packets constituting the S_I-picture,is recorded as ‘I_Start_Sub’ 1600.

In FIG. 15 (B), since the number of packets corresponding to‘I_Pic_Size’ 503 is ‘13 (packets)’, the size ID ‘3’ is recorded in‘I_Pic_Size’ 503 in the fourth embodiment. The number of packetscorresponding to ‘I_Pic_Size_Sub’ 1200 is ‘6 (packets)’ in FIG. 15 (A),but since size ID ‘3’ is recorded in ‘I_Pic_Size’ 503, fifteen of thesenineteen packets will be read from the optical disc 102. The size IDrecorded as ‘I_Pic_Size_Sub’ 1200 only has to cause four packets to beread from the optical disc 102. In FIG. 15 (B), accordingly, the size ID‘1’ is recorded as ‘I_Pic_Size_Sub’ 1200. Since the number of packetscorresponding to ‘I_Start_Sub’ 1600 in FIG. 19 (A) is ‘9 (packets)’, thesize ID ‘2’ is recorded as ‘I_Start_Sub’ 1600.

Next, the operation of the reproducing apparatus 100 in a trickreproduction mode will be described. In the following description,explanations of operations explained in the first to third embodimentswill be omitted; only different operations will be described.

From ‘PTS_GOP_Start’ 501 and ‘SPN_GOP_Start’ 502, the system controlunit 101 detects the first V_main packet among the V_main packetsconstituting the M_I-picture corresponding to the entry point to beaccessed next. The system control unit 101 acquires a first size IDrecorded in ‘I_Pic_Size’ 503, a second size ID recorded in‘I_Pic_Size_Sub’ 1200, and a size ID recorded in ‘I_Start_Sub’ 1600(referred to below as the third size ID). With reference to theI-picture size table 1500 as above, the system control unit 101calculates the sum (also referred to below as the total number ofpackets) of the maximum number of packets corresponding to the firstsize ID (e.g., 15 packets when this size ID is ‘3’) and the maximumnumber of packets corresponding to the second size ID.

For example, in FIG. 15 (B), the system control unit 101 adds ‘15(packets)’, the maximum number of packets corresponding to the firstsize ID, and ‘5 (packets)’, the maximum number of packets correspondingto the second size ID, to find that among the packets to be read, theterminal packet is located at the twentieth packet position from theV_main packet corresponding to ‘SPN_GOP_Start’ 502. Also, from the thirdsize ID ‘2’, the system control unit 101 finds that the of the packetsto be read, the leading packet is located at the sixth packet position(the minimum number of packets corresponding to the third size ID ‘2’)from the V_main packet corresponding to ‘SPN_GOP_Start’ 502.

The system control unit 101 controls the reproducing drive unit 103 toread packets from the optical disc 102 from the leading V_sub packetdetected by ‘I_Start_Sub’ 1600 to the terminal V_sub packet detected by‘I_Pic_Size_Sub’ 1200.

As described above, in the optical disc 102 according to the fourthembodiment, the amount of information in the access point managementtable can be reduced by recording size IDs in ‘I_Pic_Size’ 503,‘I_Pic_Size_Sub’ 1200, and ‘I_Start_Sub’ 1600. In particular, the amountof information needed to retrieve S_I-pictures can be reduced, ascompared with the third embodiment.

Whether to use the access point management table in the third embodimentor the access point management table in the fourth embodiment in theoptical disc 102 can be determined in the same manner as whether to usethe access point management table in the first embodiment or the accesspoint management table in the second embodiment was determined.

Although only I-pictures were described as being reproduced in the trickreproduction modes in the first to fourth embodiments, P-pictures aswell as I-pictures may be reproduced during trick reproduction. Asmoother reproduced video image (display) can be obtained by performingtrick reproduction using both I-pictures and P-pictures. If P-picturesare used, the information recorded in the access point management tablesdescribed in the first to fourth embodiments is similarly provided forP-pictures. Specifically, the position of the first packet among theV-packets constituting a P-picture may be expressed by a relative numberof packets from the last V-packet constituting the I-picture.

Although the first to fourth embodiments were described as using GOPsdefined in the MPEG-2 standard, the subject matter described in thefirst to fourth embodiments is applicable whenever access points areconstructed from compression units begin with an I-picture. Therefore,the invention can be applied to streams generated according to othercoding and compression methods, such as MPEG-4 or VC-1.

What is claimed is:
 1. A playback method for reproducing a videoinformation stream recorded on a medium, said video information streamcomprising a plurality of video information units each of which includesan intra coded I-picture, a predictive coded P-picture and abidirectionally-predictive coded B-picture, said video informationstream including a first video information stream representing a primaryvideo sequence, a second video information stream representing secondaryvideo sequence which is presented with said primary video sequence andan access point map which includes access point information andI-picture size information of said first video information stream andsaid second video information stream; said method comprising steps of:identifying a closest one of I-pictures preceding a start picturecorresponding to a start point of playback for said first videoinformation stream and a second video information stream; locating aposition and recognizing a data size of identified I-picture for saidfirst video information stream and said second video information streamby referring to said access point map, said I picture size informationrepresents the range of I-picture size; decoding said identifiedI-picture for said first video information stream and said second videoinformation stream; and decoding said start picture using decodedI-picture as a reference picture for said first video information streamand said second video information stream.
 2. A playback method accordingto claim 1, wherein said access point map includes PTS information ofsaid first video information stream and said second video informationstream, and a PTS value of an I-picture of said first video informationstream is same as that of a corresponding I-picture of said second videoinformation stream.
 3. A playback method according to claim 1, whereinan I-picture of said first video information stream precedes acorresponding I-picture of said second video information stream.
 4. Aplayback device for reproducing a video information stream recorded on amedium, said video information stream comprising a plurality of videoinformation units each of which includes an intra coded I-picture, apredictive coded P-picture and a bidirectionally-predictive codedB-picture, said video information stream including a first videoinformation stream representing a primary video sequence, a second videoinformation stream representing secondary video sequence which ispresented with said primary video sequence and an access point map whichincludes access point information and I-picture size information of saidfirst video information stream and said second video information stream;said playback device comprising: an I-picture identifying unit foridentifying a closest one of I-pictures preceding a start picturecorresponding to a start point of playback for said first videoinformation stream and a second video information stream; an I-pictureposition locating unit for locating a position of identified I-picturefor said first video information stream and said second videoinformation stream by referring to said access point map, said I picturesize information represents the range of I-picture size; an I-picturesize recognizing unit for recognizing a data size of identifiedI-picture for said first video information stream and said second videoinformation stream by referring to said access point map; a firstdecoding unit for decoding said identified I-picture for said firstvideo information stream and said second video information stream; and asecond decoding unit for decoding said start picture using decodedI-picture as a reference picture for said first video information streamand said second video information stream.
 5. A playback device accordingto claim 4, wherein said access point map includes PTS information ofsaid first video information stream and said second video informationstream, and a PTS value of an I-picture of said first video informationstream is same as that of a corresponding I-picture of said second videoinformation stream.
 6. A playback device according to claim 4, whereinan I-picture of said first video information stream precedes acorresponding I-picture of said second video information stream.
 7. Arecording method for recording a video information stream on a medium,said video information stream comprising a plurality of videoinformation units each of which includes an infra coded I-picture, apredictive coded P-picture and a bidirectionally-predictive codedB-picture, said video Information stream including a first videoinformation stream representing a primary video sequence, a second videoinformation stream representing secondary video sequence which ispresented with said primary video sequence and an access point map whichincludes access point information and I-picture size information of saidfirst video information stream and said second video information stream,comprising: a processor that processes the video information steam andrecords the video information stream on a designated location of saidmedium, wherein during playback a closest one of I-pictures preceding astart picture corresponding to a start point of playback for said firstvideo information stream and a second video information stream isidentified, and a position located and a data size recognized ofidentified I-picture for said first video information stream and saidsecond video information stream by referring to said access point map,and said I picture size information represents the range of I-picturesize.
 8. A recording method according to claim 7, wherein said accesspoint map includes PTS information of said first video informationstream and said second video information stream, and a PTS value of anI-picture of said first video information stream is same as that of acorresponding I-picture of said second video information stream.
 9. Arecording method according to claim 7, wherein an I-picture of saidfirst video information stream precedes a corresponding I-picture ofsaid second video information stream.
 10. A non-transitory mediumcontaining a video information stream, said video information streamcomprising a plurality of video information units each of which includesan intra coded I-picture, a predictive coded P-picture and abidirectionally-predictive coded B-picture, said video informationstream including a first video information stream representing a primaryvideo sequence, a second video information stream representing secondaryvideo sequence which is presented with said primary video sequence andan access point map which includes access point information andI-picture size information of said first video information stream andsaid second video information stream, wherein a playback deviceidentifies a closest one of I-pictures preceding a start picturecorresponding to a start point of playback for said first videoinformation stream and a second video information stream and locates aposition and recognizes a data size of identified I-picture for saidfirst video information stream and said second video information streamby referring to said access point map, and said I picture sizeinformation represents the range of I-picture size.
 11. A non-transitorymedium according to claim 10, wherein said access point map includes PTSinformation of said first video information stream and said second videoinformation stream, and a PTS value of an I-picture of said first videoinformation stream is same as that of a corresponding I-picture of saidsecond video information stream.
 12. A non-transitory medium accordingto claim 10, wherein an I-picture of said first video information streamprecedes a corresponding I-picture of said second video informationstream.